Organic light emitting device

ABSTRACT

An organic light emitting device including a first electrode; a self-assembled monolayer on the first electrode; a hole control layer on the self-assembled monolayer; a light emitting layer on the hole control layer; an electron control layer on the light emitting layer; and a second electrode on the electron control layer, wherein the self-assembled monolayer includes a plurality of organic molecules, each of the plurality of organic molecules having a head bonded to the first electrode, a terminal end adjacent to the hole control layer, and a tail connecting the head with the terminal end.

CROSS-REFERENCE TO RELATED APPLICATION

Korean Patent Application No. 10-2016-0021384, filed on Feb. 23, 2016,in the Korean Intellectual Property Office, and entitled: “Organic LightEmitting Device,” is incorporated by reference herein in its entirety.

BACKGROUND

1. Field

Embodiments relate to an organic light emitting device.

2. Description of the Related Art

Organic light emitting devices are self light emitting type elements,and organic light emitting displays (OLED) including such organic lightemitting devices have wide viewing angles and excellent contrast.Moreover, such organic light emitting displays have the advantages offast response time, high brightness, and low driving voltage.

Organic light emitting devices are being developed into variousconfigurations. Organic light emitting devices achieve color through amechanism in which holes and electrons injected into a first electrodeand a second electrode recombine in a light emitting layer to emitlight. The light is emitted when excitons generated by the recombinationof the injected holes and electrons fall to the ground state.

SUMMARY

Embodiments are directed to an organic light emitting device

The embodiments may be realized by providing an organic light emittingdevice including a first electrode; a self-assembled monolayer on thefirst electrode; a hole control layer on the self-assembled monolayer: alight emitting layer on the hole control layer; an electron controllayer on the light emitting layer; and a second electrode on theelectron control layer, wherein the self-assembled monolayer includes aplurality of organic molecules, each of the plurality of organicmolecules having a head bonded to the first electrode, a terminal endadjacent to the hole control layer, and a tail connecting the head withthe terminal end.

At least two organic molecules of the plurality of organic molecules mayhave tails that are of different lengths from each other.

The tail may extend orthogonally relative to a surface of the firstelectrode.

The terminal end may be chemically bonded with the hole control layer.

The hole control layer may include an anisotropic compound in which amolecular length in one direction is longer than a molecular length in aanother direction that is perpendicular to the one direction.

A long axis of the anisotropic compound may extend orthogonally relativeto a surface of the first electrode, the long axis extending in the onedirection.

The anisotropic compound may be one of the following Compounds 1 to 8:

The head may include a phosphonic acid group or a silane group.

The tail may include a substituted or unsubstituted alkylene grouphaving a carbon number of 1 to 20.

The carbon number of the alkylene group in one organic molecule of theplurality of organic molecules may be different from the carbon numberof the alkylene group in another organic molecule of the plurality oforganic molecules.

The terminal end may include hydrogen, a substituted or unsubstitutedalkyl group having 1 to 5 carbon atoms, or a substituted orunsubstituted aromatic group having 6 to 30 carbon atoms for forming aring.

The terminal end may include the substituted or unsubstituted aromaticgroup having 6 to 30 ring carbon atoms, and the aromatic group may be aphenyl group, a naphthalene group, or an anthracene group.

The self-assembled monolayer may include 8-alkylphosphonic acid and18-alkylphosphonic acid.

The embodiments may be realized by providing

an organic light emitting device including a first electrode; aself-assembled monolayer on the first electrode; a hole control layer onthe self-assembled monolayer; a light emitting layer on the hole controllayer; an electron control layer on the light emitting layer; and asecond electrode on the electron control layer, wherein theself-assembled monolayer includes a plurality of organic molecules, eachorganic molecule of the plurality of organic molecules beingindependently represented by Formula 1,

wherein, in Formula 1, X is a phosphonic acid group or a silane group, Yis hydrogen, a substituted or unsubstituted alkyl group having 1 to 5carbon atoms, or a substituted or unsubstituted aromatic group having 6to 30 carbon atoms for forming a ring, and n is an integer of 2 to 20.

The plurality of organic molecules may be disposed such that X ofFormula 1 is bonded with the first electrode and Y of Formula 1 isadjacent to the hole control layer.

The plurality of organic molecules may include a first organic moleculein which n=n1 and a second organic molecule in which n=n2, and n1 and n2may be integers that are different from each other.

n1 and n2 may satisfy |n1−n2|≧10.

Y may be a phenyl group, a naphthalene group, or an anthracene group.

The hole control layer may include an anisotropic compound in which alength in a long axis direction of the anisotropic compound differs froma length in a short axis direction of the anisotropic compound; and Y ofFormula 1 may be chemically bonded with the anisotropic compound.

The long axis direction of the anisotropic compound may be orthogonal toa surface of the first electrode.

BRIEF DESCRIPTION OF THE DRAWINGS

Features will become apparent to those of ordinary skill in the art bydescribing in detail exemplary embodiments with reference to theattached drawings in which:

FIG. 1 illustrates a cross-sectional view of an organic light emittingdevice according to an embodiment;

FIG. 2 illustrates an expanded view of a self-assembled monolayer in thecross-sectional view of the organic light emitting device of FIG. 1;

FIG. 3A schematically illustrates an organic molecule according to anembodiment;

FIG. 3B schematically illustrates the arrangement of a plurality oforganic molecules according to an embodiment;

FIG. 4 exemplarily illustrates an anisotropic compound included in ahole control layer according to an embodiment;

FIGS. 5A to 5D illustrate graphs showing the results of measuring theoptical properties of an anisotropic compound;

FIG. 6 schematically illustrates the bonding relationship between acompound in a hole layer and an organic molecule according to anembodiment;

FIG. 7A illustrates x-ray analysis results of an organic light emittingdevice in which a self-assembled monolayer is omitted;

FIG. 7B illustrates x-ray analysis results of an organic light emittingdevice including a self-assembled monolayer according to an embodiment;

FIG. 8 illustrates a perspective view of a display device according toan embodiment;

FIG. 9 illustrates a circuit diagram of a pixel included in a displaydevice according to an embodiment;

FIG. 10 illustrates a plan view of a pixel included in a display deviceaccording to an embodiment; and

FIG. 11 illustrates a cross-sectional view along line I-I′ of FIG. 10.

DETAILED DESCRIPTION

Example embodiments will now be described more fully hereinafter withreference to the accompanying drawings; however, they may be embodied indifferent forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey exemplary implementations to those skilled in the art.

In the drawing figures, the dimensions of layers and regions may beexaggerated for clarity of illustration. In addition, it will also beunderstood that when a layer is referred to as being “between” twolayers, it can be the only layer between the two layers, or one or moreintervening layers may also be present. Like reference numerals refer tolike elements throughout.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another element. For example, a first element could betermed a second element, and similarly, a second element may be termed afirst element. Singular forms are intended to include the plural formsas well, unless the context clearly indicates otherwise.

In the specification, terms such as “includes” or “has” specify thepresence of stated features, numbers, steps, operations, elements,components, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, steps,operations, elements, components, and/or combinations thereof. Moreover,when an element such as a layer, film, area, plate, etc. is referred toas being “on” another element, it can be “directly on” the otherelement, or intervening elements may also be present. When an elementsuch as a layer, film, area, plate, etc. is referred to as being “under”another element, it can be “directly under” the other element, orintervening elements may also be present.

Hereinafter, an organic light emitting device according to embodimentswill be described in detail with reference to the accompanying drawings.

FIG. 1 illustrates a cross-sectional view of an organic light emittingdevice OEL according to an embodiment. The organic light emitting deviceOEL according to an embodiment may be a sequentially laminated,laminated-type organic light emitting device OEL. Referring to thedrawings, the organic light emitting device OEL may include, e.g., afirst electrode EL1, a hole control layer HCL, a self-assembledmonolayer SAM, a light emitting layer EML, an electron control layerECL, and a second electrode EL2.

The first electrode EL1 or the second electrode EL2 may be formed of ametal alloy or a conductive compound. The first electrode EL1 and thesecond electrode EL2 may be disposed facing each other, and a pluralityof organic layers may be disposed between the first electrode EL1 andthe second electrode EL2. The plurality of organic layers may include,e.g., the self-assembled monolayer SAM, the hole control layer HCL, thelight emitting layer EML, and the electron control layer ECL.

The first electrode EL1 or the second electrode EL2 may be atransmissive electrode, a semi-transmissive electrode, or a reflectiveelectrode. When the first electrode EL1 or the second electrode EL2 is atransmissive electrode, the first electrode EL1 or the second electrodeEL2 may be formed of a transparent metal oxide, e.g., indium tin oxide(ITO), indium zinc oxide (IZO), zinc oxide (ZnO), or indium tin zincoxide (ITZO), or the like.

In an implementation, the first electrode EL1 or the second electrodeEL2 may be a semi-transmissive electrode or a reflective electrode. Thefirst electrode EL1 or the second electrode EL2 may include silver (Ag),magnesium (Mg), aluminum (Al), platinum (Pt), palladium (Pd), gold (Au),nickel (Ni), neodymium (Nd), iridium (Ir), chrome (Cr), or mixturesthereof. In an implementation, the first electrode EL1 or the secondelectrode EL2 may be a layer including a compound of lithium (Li),calcium (Ca), lithium fluoride (LiF)/calcium (Ca), LiF/Al, bariumfluoride (BaF), barium (Ba), Ag/Mg, and the like, or mixtures thereof.

In an implementation, in the organic light emitting device according toan embodiment, the first electrode EL may be an anode and the secondelectrode EL2 may be a cathode. In an implementation, the firstelectrode EL1 or the second electrode EL2 may be formed of a pluralityof layers. The first electrode EL1 or the second electrode EL2 may beprovided using a sputtering method or a vacuum deposition method and thelike.

In an implementation, when the first electrode EL1 is a transparentelectrode and the second electrode EL2 is a reflective electrode, theorganic light emitting device may be a bottom emission type. The organiclight emitting device may be a double-sided light emitting type whenboth the first electrode EL1 and the second electrode EL2 aretransparent electrodes, and a top emission type when the first electrodeEL1 is a reflective electrode and the second electrode EL2 is atransparent electrode.

In the organic light emitting device OEL, a self-assembled monolayer SAMmay be disposed on the first electrode EL1. The self-assembled monolayerSAM may be formed between the first electrode EL1 and the hole controllayer HCL, and may perform the function of adjusting the arrangement ofthe hole control layer HCL. The arrangement relationship between theself-assembled monolayer SAM and the hole control layer HCL will bedescribed below.

The hole control layer HCL may be disposed on the self-assembledmonolayer SAM. The hole control layer HCL may be a hole transport layer.In an implementation, the hole control layer HCL may be divided into ahole injection layer and a hole transport layer. In an implementation,the hole control layer HCL may further include at least one of a bufferlayer or an electron blocking layer.

The hole control layer HCL may be, e.g., a single layer formed of asingle material, a single layer formed of a plurality of differentmaterials, or have a multi-layered structure including a plurality oflayers formed of a plurality of different materials.

For example, the hole control layer HCL may have the structure of asingle layer formed of a plurality of different materials, or astructure in which the hole injection layer/hole transport layer, thehole injection layer/hole transport layer/buffer layer, the holeinjection layer/buffer layer, the hole transport layer/buffer layer, orthe hole injection layer/hole transport layer/electrode blocking layerare sequentially laminated from the first electrode EL1.

The hole control layer HCL may be formed using various methods such as avacuum deposition method, a spin coating method, a casting method, aLangmuir-Blodgett method, an inkjet printing method, a laser printingmethod, or a laser induced thermal imaging (LITI) method, and the like.

When the hole control layer HCL includes the hole injection layer, thehole control layer may include, e.g., a phthalocyanine compound such ascopper phthalocyanine; orn,n′-diphenyl-n,n′-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4′-diamine(DNTPD),4,4′,4″-tris(3-methylphenylphenylamino) triphenylamine(m-MTDATA),4,4′4″-tris(n,n-diphenylamino)triphenylamine(TDATA),4,4′,4″-tris {n,-(2-naphthyl)-n-phenylamino}-triphenylamine(2TNATA),poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate)(PEDOT/PSS),polyaniline/dodecylbenzenesulfonic acid(PANI/DBSA),polyaniline/camphor sulfonicacid (PANI/CSA), or(polyaniline)/poly(4-styrenesulfonate) (PANI/PSS), or the like.

When the hole control layer HCL includes the hole transport layer, thehole control layer HCL may include, e.g., a carbazole-based derivativesuch as n-phenylcarbazole or polyvinylcarbazole; a fluorine-basedderivative; a triphenylamine-based derivative such asn,n′-bis(3-methylphenyl)-n,n′-diphenyl-[1,1-biphenyl]-4,4′-diamine (TPD)or 4,4′,4″-tris(n-carbazolyl)triphenylamine (TCTA); orn,n′-di(1-naphthyl)-n,n′-diphenylbenzidine (NPB), 4,4′-cyclohexylidenebis[n,n-bis(4-methylphenyl)benzenamine] (TAPC), or the like.

The thickness of the hole control layer HCL may be, e.g., about 10 nm toabout 1000 nm. When the thickness of the hole control layer HCLsatisfies the above range, desirable hole transport properties may beobtained without a substantial increase in driving voltage.

In addition to the materials mentioned above, the hole control layer HCLmay further include, e.g., a charge generating material to help improveelectrical conductivity. The charge generating material may be uniformlyor non-uniformly dispersed in the hole control layer HCL. The chargegenerating material may be, e.g., a p-dopant. The p-dopant may be one ofa quinone derivative, a metal oxide, or a cyano group-containingcompound. For example, the p-dopant may be a quinone derivative such astetracyanoquinodimethane (TCNQ) or2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F4-TCNQ), or a metal oxidesuch as a tungsten oxide or a molybdenum oxide.

As described above, the hole control layer HCL may further include atleast one of the buffer layer or the electron blocking layer. The bufferlayer may help increase light emitting efficiency by compensating for aresonance distance which depends on the wavelength of light emitted fromthe light emitting layer EML. A material included in the hole controllayer HCL may be used as a material included in the buffer layer. Theelectron blocking layer is a layer having the role of helping to preventthe injection of electrons from the electron control layer ECL into thehole control layer HCL.

The light emitting layer EML may be provided on the hole control layerHCL. The light emitting layer EML may have a single-layered structure ora multi-layered structure including a plurality of layers. The lightemitting layer may be formed using various methods including a vacuumdeposition method, a spin coating method, a casting method, aLangmuir-Blodgett method, an inkjet printing method, a laser printingmethod, or a laser induced thermal imaging (LITI) method, and the like.

The light emitting layer EML may be formed of at least one host materialand at least one dopant material. The dopant included in the lightemitting layer EML may be a red, green, or blue dopant.

In an implementation, Bt₂Ir(acac) or Ir(piq)₃ and the like may be usedas the red dopant. In an implementation, Ir(ppy)₃, Ir(ppy)₂(acac), orIr(mppy)₃ and the like may be used as the green dopant, while FIrpic orDPAVBi and the like may be used as the blue dopant. CBP, mCP, TCTA,TPBI, or Alq₃ and the like may be used as the host material. In animplementation, the light emitting layer EML may be provided to athickness of about 5 nm to about 100 nm.

The electron control layer ECL may be disposed on the light emittinglayer EML. In an implementation, the electron control layer ECL mayinclude an electron transport layer and an electron injection layer. Inan implementation, the electron control layer ECL may further include ahole blocking layer.

For example, the electron control layer ECL may have a structure inwhich the electron transport layer/electron injection layer or the holeblocking layer/electron transport layer/electron injection layer aresequentially laminated from the light emitting layer EML, or have asingle-layered structure in which at least two of such layers are mixed.

The electron control layer ECL may be formed using various methods suchas a vacuum deposition method, a spin coating method, a casting method,a Langmuir-Blodgett method, an inkjet printing method, a laser printingmethod, or a laser induced thermal imaging (LITI) method, and the like.

When the electron control layer ECL includes the electron transportlayer, the electron control layer may include, e.g.,tris(8-hydroxyquinolinato)aluminum (Alq3),1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi),2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP),4,7-diphenyl-1,10-phenanthroline (Bphen),3-(4-biphenylyl)-4-phenyl-5-tert-butylphenyl-1,2,4-triazole (TAZ),4-(naphthalen-1-yl)-3,5-diphenyl-4h-1,2,4-triazole (NTAZ),2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (tBu-PBD),bis(2-methyl-8-quinolinolato-n1,o8)-(1,1′-biphenyl-4-olato)aluminum(BAlq), berylliumbis(benzoquinolin-10-olate) (Bebq2),9,10-di(naphthalene-2-yl)anthracene (ADN), or mixtures thereof. Thethickness of the electron transport layer may be about 10 nm to about100 nm, e.g., about 15 nm to about 50 nm. When the thickness of theelectron transport layer satisfies the above range, desirable electrontransport properties may be obtained without a substantial increase indriving voltage.

When the electron control layer ECL includes the electron injectionlayer, e.g., lithium fluoride (LiF), lithium quinolate (LiQ), lithiumoxide (Li₂O), barium oxide (BaO), sodium chloride (NaCl), cesiumfluoride (CsF), a lanthanum group metal such as ytterbium (Yb), or ahalogenated metal such as rubidium chloride (RbCl) or rubidium iodide(RbI) and the like may be used in the electron control layer ECL. In animplementation, the electron injection layer may be formed of a materialin which an electron transport material is mixed with an electricallyinsulative organo metal salt. The organo metal salt may be a materialhaving an energy band gap of at least about 4 eV. In an implementation,the organo metal salt may include metal acetate, metal benzoate, metalacetoacetate, metal acetylacetonate, or metal stearate. The thickness ofthe electron injection, layer may be about 0.1 nm to about 10 nm, orabout 0.3 nm to about 9 nm. When the thickness of the electron injectionlayer satisfies the above range, desirable electron injection propertiesmay be obtained without a substantial increase in driving voltage.

As described above, the electron control layer ECL may include the holeblocking layer. The hole blocking layer may include, e.g., at least oneof 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) or4,7-diphenyl-1,10-phenanthroline (Bphen). The thickness of the holeblocking layer may be about 2 nm to about 100 nm, e.g., about 3 nm toabout 30 nm. When the thickness of the hole blocking layer satisfies theabove range, excellent hole blocking properties may be obtained withouta substantial increase in driving voltage.

FIG. 2 illustrates an expanded view of DP in the cross-sectional view ofthe organic light emitting device OEL illustrated in FIG. 1, wherein DPis a region that includes a portion of the self-assembled monolayer SAM,and the hole control layer HCL and first electrode EL1 sandwiching thisportion of the self-assembled monolayer SAM. FIG. 3A schematicallyillustrates the structure of one organic molecule OM among a pluralityof organic molecules forming a self-assembled monolayer. FIG. 3Bschematically illustrates an embodiment in which the plurality oforganic molecules OM are disposed on the first electrode EL.

Referring to FIG. 2, the self-assembled monolayer SAM may include theplurality of organic molecules OM. The plurality of organic molecules OMmay form a single layer on the first electrode EL1. For example, theself-assembled monolayer SAM may be a single molecular layer formed ofthe plurality of organic molecules OM. In an implementation, theself-assembled monolayer SAM may be a single layer of the plurality oforganic molecules OM arranged on the first electrode EL1 or may includetwo or three layers formed by laminating the plurality of organicmolecules OM.

Each of the plurality of organic molecules OM forming the self-assembledmonolayer SAM may include a head part or head HD, a tail part or tailTL, and a terminal end part or terminal end FG. The plurality of organicmolecules OM may be disposed such that each of the heads HD is bonded tothe first electrode EL1 and each of the terminal ends FG is adjacent tothe hole control layer HCL. The tail TL may be a part connecting betweenthe head HD with the terminal end FG.

In an embodiment, the self-assembled monolayer SAM may include theplurality of organic molecules OM represented by Formula 1, below. In animplementation, in Formula 1. X may be, e.g., a phosphonic acid group ormoiety or a silane group or moiety. Y may be, e.g., hydrogen, asubstituted or unsubstituted alkyl group or moiety having 1 to 5 carbonatoms, or a substituted or unsubstituted aromatic group or moiety having6 to 30 ring carbon atoms, and n may be an integer of, e.g., 2 to 20.

In Formula 1, “substituted” indicates that at least one hydrogen atom ina functional group is substituted or replaced with at least one type ofsubstituent selected from the group containing halogen atoms (F, Br, Cl,or I), hydroxy groups, thiol groups, nitro groups, cyano groups, aminogroups, amidino groups, hydrazine groups, hydrazone groups, carboxylgroups, substituted or unsubstituted alkoxy groups, substituted orunsubstituted thioether groups (SR₁₀, where R₁₀ is a C1 to C10 alkylgroup), substituted or unsubstituted sulfone groups (SO₂R₁₁, where R₁₁is a C1 to C10 alkyl group), substituted or unsubstituted alkyl groups,substituted or unsubstituted alkenyl groups, substituted orunsubstituted alkynyl groups, substituted or unsubstituted cycloalkylgroups, substituted or unsubstituted cycloalkenyl groups, substituted orunsubstituted cycloalkynyl groups, substituted or unsubstituted arylgroups, and substituted or unsubstituted hetero-ring groups.

In the plurality of organic molecules OM, each of the heads HD maychemically bond with the first electrode EL1. The head HD may be or mayinclude, e.g., a phosphonic acid or silane. In an implementation, thehead HD may include other reactive groups capable of forming a chemicalbond with the first electrode EL1. For example, the head HD may form acovalent bond with a conductive material in the first electrode EL1. Thehead HD may be a part corresponding to X in Formula 1. For example, X inFormula 1 may be a part that bonds with the first electrode EL1. Forexample, the group or moiety of the head HD may be a group or moietythat is in a bound state with the first electrode EL1.

In an implementation, the tail TL may be a connecting part that connectsthe head HD with the terminal end FG. The tail TL may be, e.g., analkylene group, and may be the part corresponding to

in Formula 1. A length of the organic molecule OM may be adjusted byadjusting the length of the tail TL. For example, the length of theorganic molecule OM may be adjusted by adjusting the length of analkylene group which is the tail TL. In an implementation, the length ofthe organic molecule OM may be adjusted by changing the integer n inFormula 1.

In an implementation, at least one of the hydrogen atoms in the alkylenegroup in the tail TL may be substituted or replaced with a halogen atom.In an implementation, at least one of the hydrogen atoms in

may be substituted with fluorine (F).

The terminal end FG may correspond to a functional group interactingwith other layers disposed on the self-assembled monolayer SAM. In animplementation, the terminal end FG may be or include, e.g., an aromaticgroup. In an implementation, the terminal end FG may be or include,e.g., one of a phenyl group, a naphthalene group, or an anthracenegroup. In an implementation, Y in Formula 1 may correspond to theterminal end FG of the organic molecule.

The self-assembled monolayer SAM may be formed on the first electrodeEL1 using, e.g., a deposition method. In an implementation, theself-assembled monolayer SAM may be formed by, e.g., coating the firstelectrode EL1 with a solution prepared so as to include the plurality oforganic molecules OM.

In an embodiment, at least two of the plurality of organic molecules OMincluded in the self-assembled monolayer SAM may have tails TL ofdifferent lengths from each other. The self-assembled monolayer SAM mayinclude the plurality of organic molecules OM having tails TL ofdifferent lengths from each other. In an implementation, the pluralityof organic molecules OM forming the self-assembled monolayer SAM mayinclude, e.g., two classes of organic molecules OM having tails TL ofdifferent lengths from each other, or three classes of organic moleculesOM having tails TL of different lengths from each other. In animplementation, the self-assembled monolayer SAM may also be formed of aplurality of organic molecules OM of various lengths.

In the plurality of organic molecules OM, a carbon number (e.g., numberof chain carbons) of an alkylene group in one of the tails TL may differfrom a carbon number of an alkylene group in another one of the tailsTL. In an implementation, the self-assembled monolayer SAM may includethe plurality of organic molecules OM having different integer values ofn in Formula 1.

In an implementation, the plurality of organic molecules represented byFormula 1 may include at least one of a first organic molecule in whichn=n1 and at least one of a second organic molecule in which n=n2. In animplementation, n1 and n2 may be different integers from each other.

In an implementation, the thickness of the self-assembled monolayer SAMmay be, e.g., about 2 nm to about 3 nm. It is noted that suchthicknesses are average thicknesses of the self-assembled monolayer SAM,and the self-assembled monolayer SAM may have portions of differingthickness. For example, portions of the self-assembled monolayer SAM maybe formed to be less than 2 nm thick or more than 3 nm thick.

The thickness of the self-assembled monolayer SAM may be determinedaccording to the length of the plurality of organic molecules OMarranged on the first electrode EL1. Referring to FIG. 3A, the totallength L_(OM) of the organic molecule OM is the length including thehead HD, the tail TL, and the terminal end FG. Thus, as described above,the length L_(OM) of the organic molecule may be mostly adjusted byadjusting the length L_(TL) of the tail TL. The length of the pluralityof organic molecules OM may be adjusted by adjusting the length of eachof the tails TL, and the thickness of the self-assembled monolayer SAMmay change according to the length of the tail of the plurality oforganic molecules OM arranged on the first electrode EL1.

FIG. 3B exemplarily illustrates how the plurality of organic moleculesOM are arranged by being bonded on the first electrode EL1. In animplementation, the plurality of organic molecules OM may form apredetermined angle with the first electrode EL1 and may be arranged onthe first electrode EL1. When θ is the angle between an imaginary lineDL extending in the direction of the organic molecule OM and the face ofthe first electrode EL1, θ may be at least 60 degrees. For example, θmay be 90 degrees. When θ is 90 degrees, the self-assembled monolayerSAM may be formed by disposing the plurality of organic molecules OMsuch that the tails TL are perpendicular or orthogonal to a surface ofthe first electrode E1.

The self-assembled monolayer SAM may be formed on the first electrodeEL1 and may modify the surface properties of the first electrode EL1.The self-assembled monolayer SAM may be between the first electrode EL1and an organic film layer, and may help adjust the arrangement of theorganic film layer on the first electrode EL1.

In an implementation, the self-assembled monolayer SAM may be betweenthe first electrode EL1 and the hole control layer HCL and may helpadjust the arrangement of the hole control layer HCL. For example, theself-assembled monolayer SAM may perform an alignment function foradjusting the arrangement of the hole control layer HCL through physicalor chemical actions.

For example, the self-assembled monolayer may help arrange an organiccompound in the hole control layer HCL by providing physical ridges andvalleys formed by the plurality of organic molecules OM having differentlengths. In an implementation, the self-assembled monolayer SAM mayinclude the plurality of organic molecules OM, which are chemicallybonded with the organic compound in the hole control layer HCL, andarrange the organic compound in the hole control layer HCL.

As illustrated in FIG. 2, in an embodiment, the plurality of organicmolecules OM having tails TL of different lengths may be arranged on thefirst electrode EL1, and an interface IFL between the self-assembledmonolayer SAM and the hole control layer HCL may have curves.

The self-assembled monolayer SAM may include the plurality of organicmolecules OM having different lengths, and the surface of theself-assembled monolayer SAM may have fine ridges and valleys. Forexample, the plurality of organic molecules OM having different lengthsmay be randomly arranged on the first electrode EL1 such that thetrajectory of the interface IFL, which is an imaginary line connectingthe tails of the plurality of organic molecules OM, is not flat but hascurves in accordance with the differences in length amongst the organicmolecules OM arranged on the first electrode EL1.

In an implementation, the formation of physical ridges and valleys inthe interface IFL between the self-assembled monolayer SAM and the holecontrol layer HCL may become easier as the differences in length amongstthe tails TL becomes larger in the self-assembled monolayer SAM formedof the plurality of organic molecules OM having tails TL of differentlengths.

For example, when the self-assembled monolayer SAM includes theplurality of organic molecules represented by Formula 1, theself-assembled monolayer SAM may include at least one of the firstorganic molecule in which n=n1 and at least one of the second organicmolecule in which n=n2. In an implementation, n1 and n2 are differentintegers, and the difference between n1 and n2 may be at least 10. Whenthe difference between n1 and n2 is at least 10, randomly arrangedpluralities of the first organic molecules and the second organicmolecules may easily form physical ridges and valleys on the surface ofthe self-assembled monolayer, and thus the interface between theself-assembled monolayer and the hole control layer may be formed toinclude a large number of physical ridges and valleys. Accordingly, thephysical ridges and valleys formed due to the differences in lengthamongst the tails may cause the molecules in the hole control layer tobe randomly arranged on the self-assembled monolayer.

In an implementation, the plurality of organic molecules OM forming theself-assembled monolayer SAM may include, e.g., 8-alkylphosphonic acidand 18-alkylphosphonic acid. In an implementation, the self-assembledmonolayer SAM may include the plurality of organic molecules representedby Formula 1 and having alkylene groups of different carbon numbers.

The surface of the self-assembled monolayer SAM may have curves, and thehole control layer HCL on the self-assembled monolayer SAM may bedisposed along the curves provided by the self-assembled monolayer SAM.

In an implementation, the hole control layer HCL may include ananisotropic compound HM. For example, the anisotropic compound HMincluded in the hole control layer HCL may be randomly arranged alongthe physical ridges and valleys on the surface of the self-assembledmonolayer SAM.

FIG. 4 exemplarily illustrates the anisotropic compound HM according toan embodiment. The length L1 in which the anisotropic compound HM isextended in one direction (e.g., DR1) may be longer than the length L2in which the anisotropic compound HM is extended in another direction(e.g., DR2) perpendicular to the one direction. For example, theanisotropic compound HM may be a hole transport material in which thelength L1 in a long axis direction (aligned with the one direction)differs from the length L2 in a short axis direction (aligned with theother direction).

Examples of the anisotropic compound HM included in the hole controllayer HCL are shown below. In an implementation, the hole control layerHCL may include any one of Compounds 1 to 8, below.

FIGS. 5A to 5D illustrate graphs showing the refractive indices andextinction coefficients of the anisotropic compounds HM above. FIGS. 5A,5B, 5C, and 5D illustrate graphs showing the refractive index andextinction coefficient of Compound 2, 3, 4, and 5, respectively. Here,n_(o) and k_(o) respectively indicate the refractive index andextinction coefficient in the horizontal axis direction, and n_(e) andk_(e) respectively indicate the refractive index and extinctioncoefficient in the vertical axis direction.

Referring to FIGS. 5A to 5D, it may be seen that n_(o)>n_(e) andk_(o)>k_(e). Therefore, it may be seen from the graphs in FIGS. 5A to 5Dthat the anisotropic compound HM included in the hole control layer HCLis optically anisotropic.

In addition, it may be seen that the difference between n_(o) and n_(e)and between k_(o) and k_(e) increases going from FIG. 5A to FIG. 5D. Forexample, it may be seen that the optical properties of the hole controllayer HCL may change according to the shape of the anisotropic compoundHM, and that the difference between the wavelength dependent values ofn_(o) and n_(c) increases and optical anisotropy increases as the lengthin the long axis direction of the molecules becomes relatively longer.

FIG. 6 illustrates an expanded view of the organic light emitting deviceaccording to an embodiment the first electrode EL1, the self-assembledmonolayer SAM on the first electrode EL1, and the hole control layer HCLon the self-assembled monolayer SAM. In FIG. 6, AA is a portionexemplary illustrating the bonding relationship between one of theorganic molecules OM in the self-assembled monolayer SAM and one of theanisotropic compounds HM in the hole control layer HCL. For example, inthe organic molecule OM in FIG. 6, phosphonic acid may be at the headHD, the terminal end FG may have a phenyl group, and the tail TL maycorrespond to an alkylene group. The anisotropic compound HM may be anamine compound having two phenyl groups at a terminal end thereof.

In an embodiment, the anisotropic compound HM in the hole control layerHCL may be arranged such that the long axis is perpendicular ororthogonal to the surface of the first electrode EL1. For example, theanisotropic compound HM may be arranged such that the long axis, alongwhich the length of the molecule is longer, is aligned with the firstdirection DR1, which is the thickness direction of the display device.

BA in FIG. 6 schematically illustrates the bonding relationship betweenthe anisotropic compound HM and the organic molecule OM. For example, inBA, the anisotropic compound HM in the hole control layer HCL mayundergo a chemical interaction with the terminal end FG of the organicmolecule OM forming the self-assembling monolayer SAM. For example, inthe embodiment illustrated in FIG. 6, a phenyl group, which is theterminal end FG in the organic molecule OM, may bond with one of thephenyl groups in an amine group in the anisotropic compound HM. Forexample, the oppositely polarized phenyl groups in the terminal end ofthe organic molecule and the amine group respectively, may be bondedwith each by molecular interactions. For example, a dipole-dipoleinteraction, hydrogen bond, van der Waals force, or other intermolecularforce may form the bond or attraction between the terminal end of theorganic molecule and the anisotropic compound.

In an implementation, the anisotropic compound may be arrangedorthogonal to the surface of the first electrode EL1 due to theinteraction between the end group in the anisotropic compound HMincluded in the hole control layer HCL and the terminal end FG of theplurality of organic molecules OM forming the self-assembled monolayerSAM. For example, the terminal end of the organic molecule and theanisotropic compound may be arranged through Π-Π stacking due tomolecular interactions.

In an implementation, the lengths of the tails TL of the plurality oforganic molecules OM arranged on the first electrode EL may all beidentical. In an implementation, the self-assembled monolayer SAM mayinclude at least two of the plurality of organic molecules OM havingtails TL of different lengths.

In the embodiment in FIG. 6, the anisotropic compound HM in the holecontrol layer HCL may bond with the organic molecules OM in theself-assembled monolayer SAM and be arranged orthogonal to the surfaceof the first electrode EL1.

FIG. 6 illustrates only the areas of the hole control layer HCL close tothe self-assembled monolayer SAM, and the arrangement of the anisotropiccompound HM in the remaining other areas of the hole control layer HCLmay differ from the arrangement of the anisotropic compound HM disposedclose to the self-assembled monolayer SAM. For example, the greater thedistance from the self-assembled monolayer SAM, the less thepredetermined angle between the anisotropic compounds HM and the firstelectrode EL1 may be maintained and the more random the arrangement ofthe anisotropic compounds HM.

FIG. 7A illustrates x-ray test results for verifying the arrangement ofanisotropic molecules in a hole control layer in an organic lightemitting device in which the self-assembled monolayer was omitted. FIG.7B illustrates x-ray test results verifying the arrangement of theanisotropic molecules in the hole control layer of the organic lightemitting device in an embodiment. The test results in FIGS. 7A and 7Bare results obtained using near edge x-ray absorption fine structure(NEXAFS).

FIGS. 7A and 7B compare absorption spectrum measurements according tothe incidence angle of x-rays. FIG. 7A shows an absorption spectrum forthe case in which a hole control layer is formed directly on a firstelectrode. FIG. 7B shows an absorption spectrum for an organic lightemitting device, for the case in which a self-assembled monolayer isdisposed on a first electrode, and a hole control layer is disposed onthe self-assembled monolayer. As in the embodiment in FIG. 2, theembodiment in FIG. 7B may exemplify a case in which a plurality oforganic molecules having different lengths form the self-assembledmonolayer.

FIGS. 7A and 7B respectively illustrate the results of measuring thearrangement of anisotropic compounds in a hole control layer for thecase in which the hole control layer is disposed directly on a firstelectrode and the case in which a self-assembled monolayer is disposedbetween a first electrode and the hole control layer. In the spectrumdata of FIGS. 7A and 7B, π*(C═C), σ*(C═C), and σ*(C—H) respectivelyindicate the bonding relationships in an aromatic ring.

In the case of FIG. 7A, the peaks indicating the respective bondingrelationships changed according to the angle, and in the case of FIG.7B, the degree of change according to the angle in the peaks indicatingthe respective bonding relationships was smaller than in the case ofFIG. 7A. For example, the change according to the angle may be largewhen the hole control layer is disposed directly on the first electrode,and it may be seen that the anisotropic compound is arranged in apredetermined direction. For example, in the case of FIG. 7A, the longaxis of the anisotropic compound may be arranged parallel to the firstelectrode. In comparison, in the case of FIG. 7B, the change in thespectrum according to the angle may not be large, and it may be seenthat the anisotropic compound is randomly arranged.

An embodiment may include the self-assembled monolayer and thus mayreduce the color deviation due to viewing angle. For example, when thecolor deviation due to viewing angle in the organic light emittingdevice in which the hole control layer having the anisotropic compoundis disposed directly on the first electrode is set as 100%, the colordeviation due to viewing angle may be reduced to about 82% to about 86%in cases like the embodiment in which the self-assembled monolayer isbetween the hole control layer and the first electrode.

A change in the wavelength of light according to the change in theviewing angle may follow the formula below. Here, λ(θ) indicates thewavelength according to the viewing angle, n(θ) indicates the refractiveindex according to the viewing angle, and L cos θ indicates the pathlength of the light according to the viewing angle.

λ(θ)∝n(θ)×L cos θ

When the hole control layer is on the self-assembled monolayer, thedegree to which the wavelength changes according to the viewing anglemay be reduced by making it so that the anisotropic compound forming thehole control layer is randomly arranged on the self-assembled monolayeror arranged in a direction orthogonal to the surface of the firstelectrode.

For example, according to the above relationship, even though L cos θdecreases towards the side viewing angles, when the anisotropic compoundis arranged so as to be vertically oriented, the refractive angle mayincrease according to the viewing angle. Consequently the shift to lowerwavelengths resulting from the decrease in L cos θ may be offset.Therefore, by using, as in the embodiment, the self-assembled monolayerto randomly or vertically arrange the anisotropic compound, thedeviation in color according to the change in viewing angle may bereduced compared to the case in which the absence of the self-assembledmonolayer results in a horizontal arrangement of the anisotropiccompound. The organic light emitting device according to an embodimentmay include the self-assembled monolayer and thus be capable of randomlyarranging the organic compound molecules in the hole control layer, andthe color deviation due to the viewing angle may be limited. In animplementation, by including the self-assembled monolayer having anaromatic group at an end group, the organic light emitting deviceaccording to an embodiment may arrange the organic compound molecules inthe hole control layer perpendicular to the first electrode and therebylimit the color deviation due to viewing angle.

Techniques, other than those adopting the self-assembled monolayer, forimproving viewing angle-dependent optical properties, such as methodsfor changing the light path by forming physical ridges and valleys orthrough light scattering may have an effect on the frontal brightness orcolor coordinates of an organic light emitting device. Moreover, thereflectance due to external light may also increase. In contrast, in anembodiment, the refractive index at the sides may be compensated byusing the self-assembled monolayer to adjust the arrangement of the holecontrol layer molecules, and changes to the optical properties, such asto the frontal brightness or color coordinates, may be prevented. In animplementation, the reflectance may not be increased by external light.

Hereinafter, a display device according to an embodiment which includesthe above-described organic light emitting device according to anembodiment will be described with reference to FIGS. 8 to 11.

FIG. 8 illustrates a perspective view of a display device according toan embodiment. Referring to FIG. 8, a display device 10 may include adisplay area DA and a non-display area NDA.

The display area DA displays an image. When viewed from a firstdirection DR1, which is the thickness direction of the display device10, the display area DA may have an approximately rectangular shape.

The display area DA includes a plurality of pixel areas PA. The pixelareas PA may be arranged as a matrix. The pixel areas PA may be definedby a pixel defining film (PDL in FIG. 11). The pixel areas PA mayinclude each of a plurality of pixels (PX in FIG. 9).

The non-display area NDA does not display an image. When viewed from thethickness direction DR1 of the display device 10, the non-display areaNDA may, for example, surround the display area DA. The non-display areaNDA may be adjacent to the display area DA in a second direction (forexample, DR2) and a third direction (for example, DR3) which intersectsthe second direction.

FIG. 9 illustrates a circuit diagram of one of the pixels included inthe display device according to an embodiment. FIG. 10 illustrates aplan view of one of the pixels included in the display device accordingto an embodiment, and FIG. 11 illustrates a cross-sectional view takenalong I-I′ in FIG. 10.

Referring to FIGS. 9 to 11, each of the pixels PX includes a line unitincluding a gate line GL, a data line DL, and a driving voltage lineDVL, thin film transistors TFT1 and TFT2 connected to the line unit, theorganic light emitting device OEL connected to the thin film transistorsTFT1 and TFT2, and a capacitor Cst.

Each of the pixels PX may emit light of a particular color, for example,one among a red light, a green light, or a blue light. The kind ofcolored light is not limited to the above, and may also include a cyanlight, a magenta light, a yellow light, etc.

The gate line GL extends in the second direction DR2. The data line DLextends in the third direction DR3 intersecting the gate line GL. Thedriving voltage line DVL extends in substantially the same direction asthe data line DL, that is, the third direction DR3. The gate line GLtransmits a scanning signal to the thin film transistors TFT1 and TFT2,the data line DL transmits a data signal to the thin film transistorsTFT1 and TFT2, and the driving voltage line DVL provides a drivingvoltage to the thin film transistors TFT1 and TFT2.

The thin film transistors TFT1 and TFT2 may include a driving thin filmtransistor TFT2 for controlling the organic light emitting device OELand a switching thin film transistor TFT1 which switches the drivingthin film transistor TFT2. In an embodiment, each of the pixels PX isdescribed as including two of the thin film transistors TFT1 and TFT2,and each of the pixels PX may also include one thin film transistor anda capacitor, or be provided with three or more thin film transistors andtwo or more capacitors.

The switching thin film transistor TFT1 includes a first gate electrodeGE1, a first source electrode SE1, and a first drain electrode DE1. Thefirst gate electrode GE1 is connected to the gate line GL, and the firstsource electrode SE1 is connected to the data line DL. The first drainelectrode DE1 is connected to a first common electrode CE1 through afifth contact hole CH5. The switching thin film transistor TFT1transmits to the driving thin film transistor TFT2, the data signalapplied to the data line DL according to the scanning signal applied tothe gate line GL.

The thin film transistor TFT2 includes a second gate electrode GE2, asecond source electrode SE2, and a second drain electrode DE2. Thesecond gate electrode GE2 is connected to the first common electrodeCE1. The second source electrode SE2 is connected to the driving voltageline DVL. The second drain electrode DE2 is connected to a firstelectrode EL1 through a third contact hole CH3.

The first electrode EL1 is connected with a second drain electrode DE2in the driving thin film transistor TFT2. A common voltage is applied tothe second electrode EL2, and a light emitting layer EML emits lightaccording to an output signal of the driving thin film transistor TFT2to thereby display an image. Here, the light emitted from the lightemitting layer EML may change according to the type of dopant containedin the light emitting layer.

The capacitor Cst is connected between the second gate electrode GE2 andsecond source electrode SE2 in the driving thin film transistor TFT2,and charges and maintains the data signal input into the second gateelectrode GE2 in the driving thin film transistor TFT2. The capacitorCst may include the first common electrode CE1, which is connected withthe first drain electrode DE1 through a sixth contact hole CH6, and asecond common electrode CE2, which is connected with the driving voltageline DVL.

Referring to FIGS. 10 and 11, the display device 10 according to anembodiment includes a base substrate BS on which the thin filmtransistors TFT1 and TFT2 and the organic light emitting device OEL arelaminated.

Since the display device includes the organic light emitting device OELdescribed above, descriptions of the specific features of the organiclight emitting device OEL will not be repeated below. Other features ofthe display device will be described.

In the display device, a typical base substrate BS may be used withoutparticular limit. For example, the base substrate BS may be formed of anelectrically insulative material such as a glass, a plastic, or quartz.Organic polymers forming the base substrate BS may include polyethyleneterephthalate (PET), polyethylene naphthalate (PEN), polyimide,polyethersulfone, etc. The base substrate BS may be selected byconsidering mechanical strength, thermal stability, transparency,surface smoothness, ease of handling, water resistance, etc.

A substrate buffer layer (not shown) may be provided on the basesubstrate BS. The substrate buffer layer (not shown) prevents thediffusion of contaminants to the switching thin film transistor TFT1 andthe driving thin film transistor TFT2. The substrate buffer layer (notshown) may be formed of silicon nitride (SiNx), silicon oxide (SiOx),silicon oxynitride (SiOxNy), etc., and may also be excluded depending onthe material of the base substrate BS and the process conditions.

A first semiconductor layer SM1 and a second semiconductor layer SM2 areprovided on the base substrate BS. The first semiconductor layer SM1 andthe second semiconductor layer SM2 are formed of semiconductor materialsand operate as an activation layer for the switching thin filmtransistor TFT1 and the driving thin film transistor TFT2, respectively.The first semiconductor layer SM1 and the second semiconductor layer SM2each include a source area SA, a drain area DRA, and a channel area CAprovided between the source area SA and the drain area DRA. The firstsemiconductor layer SM1 and the second semiconductor layer SM2 may eachbe formed of a material selected from among an inorganic semiconductorand an organic semiconductor. The source area SA and the drain area DRAmay be doped with an n-type dopant or a p-type dopant.

A gate insulating layer GI is provided on the first semiconductor layerSM1 and the second semiconductor layer SM2. The gate insulating layer GIcovers the first semiconductor layer SM1 and the second semiconductorlayer SM2. The gate insulating layer GI may be formed of an organicinsulating material or an inorganic insulating material.

A first gate electrode GE1 and a second gate electrode GE2 are providedon the gate insulating layer GI. The first gate electrode GE1 and thesecond gate electrode GE2 may be formed so as to respectively cover theareas corresponding to the channel area CA in the first semiconductorlayer SM1 and the channel area CA in the second semiconductor layer SM2.

An interlayer insulating layer IL is provided on the first gateelectrode GE1 and the second gate electrode GE2. The interlayerinsulating layer IL covers the first gate electrode GE and the secondgate electrode GE2. The interlayer insulating layer IL may be formed ofan organic insulating material or an inorganic insulating material.

The first source electrode SE1 and first drain electrode DE1, and thesecond source electrode SE2 and second drain electrode DE2 are providedon the interlayer insulating layer IL. The second drain electrode DE2contacts the drain area DRA in the second semiconductor layer SM2through a first contact hole CH1 formed in the gate insulating layer GIand the interlayer insulating layer IL, and the second source electrodeSE2 contacts the source area SA in the second semiconductor layer SM2through a second contact hole CH2 formed in the gate insulating layer GIand the interlayer insulating layer IL. The first source electrode SE1contacts the source area (not shown) in the first semiconductor SM1through a fourth contact hole CH4 formed in the gate insulating layer GIand the interlayer insulating layer IL, and the first drain electrodeDE1 contacts the drain area (not shown) in the first semiconductor layerSM1 through the fifth contact hole CH5 formed in the gate insulatinglayer GI and the interlayer insulating layer IL.

A passivation layer PL is provided on the first source electrode SE1 andfirst drain electrode DE1, and the second source electrode SE2 andsecond drain electrode DE2. The passivation layer PL may perform therole of a protective film that protects the switching thin filmtransistor TFT1 and the driving thin film transistor TFT2, and may alsoperform the role of a flattening film that flattens the top facethereof.

The first electrode EL1 is provided on the passivation layer PL. Thefirst electrode EL1 may be, for example, a positive electrode. The firstelectrode EL1 is connected to the second drain electrode DE2 in thedriving thin film transistor TFT2 through the third contact hole CH3formed in the passivation layer PL.

The pixel defining film PDL which partitions the pixel areas (PA in FIG.4) such that the pixel areas respectively correspond to the pixels PX isprovided on the passivation film PL. The pixel defining film PDL exposesthe top face of the first electrode EL1 and protrudes from the basesubstrate BS along the perimeters of each of the pixels PX. The pixeldefining film PDL may contain a metal fluoride compound. For example,the pixel defining film PDL may be formed of a metal fluoride compoundamong lithium fluoride (LiF), barium fluoride (BaF₂), and cesiumfluoride (CsF). When having a predetermined thickness, themetal-fluoride compound is insulative. The thickness of the pixeldefining film PDL may be, for example, about 10 nm to about 100 nm.

The organic light emitting device is provided to each of the pixel areas(PA in FIG. 8) surrounded by the pixel defining film PDL. The organiclight emitting device OEL provided is the organic light emitting deviceaccording to embodiments described above. The organic light emittingdevice may include, e.g., the first electrode EL1, the self-assembledmonolayer SAM, the hole control layer HCL, the light emitting layer EML,the electron control layer ECL, and the second electrode EL2. In animplementation, the self-assembled monolayer SAM may include, e.g., atleast two of the plurality of organic molecules having tails ofdifferent lengths. In an implementation, the self-assembled monolayerSAM may include the plurality of organic molecules having, e.g., anaromatic group in the terminal end.

The display device according to an embodiment may include the organiclight emitting device which has the self-assembled monolayer. Thus, themolecules in the hole control layer may be randomly arranged such thatthe color deviation due to viewing angle is limited. In animplementation, the display device according to an embodiment mayinclude the self-assembled monolayer having an aromatic group in an endgroup, and the color deviation due to viewing angle may be limited byarranging the molecules in the hole control layer to be perpendicular tothe first electrode.

An organic light emitting device according to an embodiment may includea self-assembled monolayer between a first electrode and a hole controllayer such that deviations in the optical properties due to viewingangle may be minimized by adjusting the arrangement of an organiccompound forming the hole control layer.

In an implementation, deviations in the optical properties due toviewing angle may be minimized without a change in the light emittingefficiency or color coordinates by changing the length of the organiccompound to thereby randomize the arrangement of the organic compound inthe hole control layer disposed on the self-assembled monolayer.

In an implementation, deviations in the optical properties due toviewing angle may be minimized without a change in the light emittingefficiency or color coordinates by chemically bonding the material inthe hole control layer with the self-assembled monolayer such that theorganic compound in the hole control layer is arranged vertically.

The embodiments may provide an organic light emitting device in whichthe color deviation due to viewing angle is minimized.

The embodiments may provide an organic light emitting device in whichthe change in optical properties according to viewing angle is minimizedby controlling the arrangement of organic compounds forming a holecontrol layer.

Example embodiments have been disclosed herein, and although specificterms are employed, they are used and are to be interpreted in a genericand descriptive sense only and not for purpose of limitation. In someinstances, as would be apparent to one of ordinary skill in the art asof the filing of the present application, features, characteristics,and/or elements described in connection with a particular embodiment maybe used singly or in combination with features, characteristics, and/orelements described in connection with other embodiments unless otherwisespecifically indicated. Accordingly, it will be understood by those ofskill in the art that various changes in form and details may be madewithout departing from the spirit and scope of the present invention asset forth in the following claims.

What is claimed is:
 1. An organic light emitting device, comprising: afirst electrode; a self-assembled monolayer on the first electrode; ahole control layer on the self-assembled monolayer; a light emittinglayer on the hole control layer; an electron control layer on the lightemitting layer; and a second electrode on the electron control layer,wherein the self-assembled monolayer includes a plurality of organicmolecules, each of the plurality of organic molecules having a headbonded to the first electrode, a terminal end adjacent to the holecontrol layer, and a tail connecting the head with the terminal end. 2.The organic light emitting device as claimed in claim 1, wherein atleast two organic molecules of the plurality of organic molecules havetails that are of different lengths from each other.
 3. The organiclight emitting device as claimed in claim 1, wherein the tail extendsorthogonally relative to a surface of the first electrode.
 4. Theorganic light emitting device as claimed in claim 1, wherein theterminal end is chemically bonded with the hole control layer.
 5. Theorganic light emitting device as claimed in claim 1, wherein the holecontrol layer includes an anisotropic compound in which a molecularlength in one direction is longer than a molecular length in a anotherdirection that is perpendicular to the one direction.
 6. The organiclight emitting device as claimed in claim 5, wherein a long axis of theanisotropic compound extends orthogonally relative to a surface of thefirst electrode, the long axis extending in the one direction.
 7. Theorganic light emitting device as claimed in claim 5, wherein theanisotropic compound is one of the following Compounds 1 to 8:


8. The organic light emitting device as claimed in claim 1, wherein thehead includes a phosphonic acid group or a silane group.
 9. The organiclight emitting device as claimed in claim 1, wherein the tail includes asubstituted or unsubstituted alkylene group having a carbon number of 1to
 20. 10. The organic light emitting device as claimed in claim 9,wherein the carbon number of the alkylene group in one organic moleculeof the plurality of organic molecules is different from the carbonnumber of the alkylene group in another organic molecule of theplurality of organic molecules.
 11. The organic light emitting device asclaimed in claim 1, wherein the terminal end includes hydrogen, asubstituted or unsubstituted alkyl group having 1 to 5 carbon atoms, ora substituted or unsubstituted aromatic group having 6 to 30 ring carbonatoms.
 12. The organic light emitting device as claimed in claim 11,wherein: the terminal end includes the substituted or unsubstitutedaromatic group having 6 to 30 ring carbon atoms, and the aromatic groupis a phenyl group, a naphthalene group, or an anthracene group.
 13. Theorganic light emitting device as claimed in claim 1, wherein theself-assembled monolayer includes 8-alkylphosphonic acid and18-alkylphosphonic acid.
 14. An organic light emitting device,comprising: a first electrode; a self-assembled monolayer on the firstelectrode; a hole control layer on the self-assembled monolayer; a lightemitting layer on the hole control layer; an electron control layer onthe light emitting layer; and a second electrode on the electron controllayer, wherein the self-assembled monolayer includes a plurality oforganic molecules, each organic molecule of the plurality of organicmolecules being independently represented by Formula 1,

wherein, in Formula 1, X is a phosphonic acid group or a silane group, Yis hydrogen, a substituted or unsubstituted alkyl group having 1 to 5carbon atoms, or a substituted or unsubstituted aromatic group having 6to 30 carbon atoms for forming a ring, and n is an integer of 2 to 20.15. The organic light emitting device as claimed in claim 14, whereinthe plurality of organic molecules are disposed such that X of Formula 1is bonded with the first electrode and Y of Formula 1 is adjacent to thehole control layer.
 16. The organic light emitting device as claimed inclaim 14, wherein: the plurality of organic molecules includes a firstorganic molecule in which n=n1 and a second organic molecule in whichn=n2, and n1 and n2 are integers that are different from each other. 17.The organic light emitting device as claimed in claim 16, wherein n1 andn2 satisfy |n1−n2|≧10.
 18. The organic light emitting device as claimedin claim 14, wherein Y is a phenyl group, a naphthalene group, or ananthracene group.
 19. The organic light emitting device as claimed inclaim 18, wherein: the hole control layer includes an anisotropiccompound in which a length in a long axis direction of the anisotropiccompound differs from a length in a short axis direction of theanisotropic compound; and Y of Formula 1 is chemically bonded with theanisotropic compound.
 20. The organic light emitting device as claimedin claim 19, wherein the long axis direction of the anisotropic compoundis orthogonal to a surface of the first electrode.